1. Field of the Invention
The present invention relates to a medical instrument used to implant seeds, such as radioactive seeds, into a patient""s body. In particular, the present invention relates to a needle spin capability for a medical instrument.
2. Description of the Related Art
For treating prostate cancer, radioactive seeds are provided to various locations within a patient""s prostate gland, by way of a medical instrument, also called a seed implantation device. Typically, a base unit which includes an ultrasound unit is used to determine the exact location of the patient""s prostate gland with respect to the base unit. The base unit is capable of being moved either towards the patient or away from the patient.
The ultrasound unit includes a probe, which is inserted into the patient""s rectum while the patient is lying on his back. A grid template is mounted onto the base unit, whereby the grid template includes a plurality of rows and columns of needle holes in which a needle can be inserted. Typically, the grid template includes a 13 by 13 matrix of needle holes, whereby adjacent holes on a row or a column are spaced 5 mm apart. Every other row is labeled with a number (e.g., 1, 2, etc.) on the grid template, and every other column is labeled with an alphabetic character (e.g., A, B, etc.). There is a direct relation between the centerline axis of the ultrasound probe and the position of the holes of the grid template.
Based on information obtained from the ultrasound unit, a needle is positioned through a particular hole (e.g., B5 hole) on the grid template, and then the needle is inserted into a region within the patient""s body in which the prostate gland is located. By using the ultrasound unit, a precise position of the proximal and distal positions (relative to the ultrasound unit) of the prostate gland can be determined and recorded. The distal position (relative to the ultrasound unit) of the prostate gland is also called the xe2x80x9czero retraction pointxe2x80x9d. Once the prostate gland position information is obtained, a seed implantation plan can be determined by a doctor, where the plan corresponds to a sequential process for injecting seeds into particular locations within the patient""s prostate gland. Such treatment is generally started by placing the end of the needle (e.g., bevel end of a bevel needle or the end of a trocar needle) at the zero retraction point, and then start applying seeds with respect to that reference point.
For a conventional seed implantation device, a needle is first placed into a particular needle hole of a grid template, and then the seed implantation device is held in place by a doctor and attached to the needle. The seed implantation device is then used to inject one or more seeds into the patient""s body through the needle. When finished with that hole, the seed implantation device is detached from the needle, and placed aside. Then, the needle is removed from the grid template, and a new needle is positioned at another needle hole of the grid template, according to the specific plan for treating the patient""s prostate gland. Alternatively, some physicians prefer to insert an entire row of needles onto the grid template, and thereby move from needle to needle. Other physicians implant all needles required at the deepest depth position, and then continue with all needles required at the next-deepest depth position, and so forth. One conventional seed implantation device is called a MICK applicator, and requires the operator to physically reposition the MICK applicator back onto a new needle positioned onto the grid template. Such an applicator is described in U.S. Pat. No. 5,860,909, entitled Seed Applicator for Use in Radiation Therapy.
The inventors have recognized a problem in that implanted seeds tend to move away from their initially implanted location towards the operator, due to actions caused by the needle moving to a next seed implant location within the patient""s body or along the needle path as it is removed once the last seed has been implanted. This moving of the seeds is undesirable.
An object of the present invention is to provide a needle spin assembly that provides for the needle to spin between seed implantation locations, so that seeds are properly positioned with a patient""s body, and do not move to undesired positions during the seed implantation procedure.
This object may be achieved by an apparatus for rotating a needle that is coupled to a medical instrument. The apparatus includes rotating means for providing rotational movement of the needle while the needle is attached to the medical instrument.
The above-mentioned object may also be achieved by an apparatus for depositing, using a medical instrument having a needle coupled thereto, at least one seed at predetermined locations with a patient""s body. The apparatus includes a cam that is configured to be coupled at a distal end to the needle, and to be coupled at a proximal end to the medical instrument, the cam including at least one helical slot provided at the distal end thereof. The apparatus also includes a collar that is configured to ride along the at least one helical slot so that the collar moves in a linear direction on the cam. The apparatus further includes a control link that is coupled to the collar and that is configured to move the collar in the linear direction upon operation of a trigger on the medical instrument. When the control link is actuated under operator control, the collar is moved in the linear direction, thereby causing the cam and the needle to rotate to thereby cause the needle to spin between seed implant positions.
The above-mentioned object may also be achieved by a method for depositing seeds into a patient for treatment of the patient, by way of a needle that is coupled to a medical instrument. The method includes a step of inserting at least one seed into a first position within the patient""s body, by way of the needle. The method also includes a step of moving the medical instrument away from the patient to thereby move the needle to a second position within the patient""s body. The method further includes a step of, simultaneously with the moving step, spinning the needle between the first position and the second position. The spinning step helps maintain the at least one seed at the first position within the patient""s body.
Needle spin allows trapped air to be vented, preventing vacuum or pressurization of the air. In addition, friction between the seeds and the needle are reduced by relative dynamic motion.